A process for the continuous production of polyurethane slabstock foam by applying a polyurethane reactive mixture in the form of a liquid foam from a substantially punctually or rotationally symmetrical source onto the conveyor belt of a slabstock foam plant is disclosed, for example, in WO 96/16782 and in European patent application 96 116 053.8, which is not a prior publication, or German application 19 627 065.0, wherein a polyurethane reactive mixture containing carbon dioxide dissolved under pressure is decompressed to form a liquid foam and is applied onto the conveyor belt of a slabstock foam plant. The conveyor belt may have a width of 2.2 m or greater.
One problem with such a process is the transverse distribution of the liquid foam (froth) over the width of the conveyor belt.
In order to solve this problem, European patent application 95 109 419.2 proposed providing a deflector for feeding the upper laminating film flat, resulting in the formation, between the upper and lower laminating film, of a channel having a substantially constant cross-section, in which, before entering the channel, the liquid foam accumulates and is distributed across the width of the conveyor belt. See also EP-A 21,564 which shows a channel with a narrowing cross-section.
Adhesion and curing of the polyurethane reactive mixture on the transverse distributor element is avoided by performing the transverse distribution using the upper laminating film because the surface of the transverse distributor element is constantly renewed. Furthermore, the motion of the lower and upper laminating films in the same direction promotes the drawing in of the froth into the channel, thus, making a substantial contribution to the transverse distribution within the channel. This counteracts any "ageing" of the froth in the accumulated material upstream from the channel.
An unsatisfactory feature of this solution is the requirement of using an upper laminating film or at least a circulating film, from which any adhering polyurethane must be removed. This problem may partly be reduced by using foils having a layer of polyethylene, silicone or similar material as proposed according to DE-A 1778946.